Crustal assimilation in the Burnt Lake metavolcanics, Grenville Province, southeastern Ontario, and its tectonic significance

Abstract

Three intimately interbedded suites sf volcanic rocks are identified geochemically in the Burnt Lake area of the Belmsnt Domain in the Central Metasedimentary Belt, and their petrogenesis is evaluated. The Burnt Lake back-arc tholeiitic suite comprises basalts similar in trace element signature to tholeiitic basalts emplaced in back-arc basins formed in continental crust. The Burnt Lake continental tholeiitic suite comprises basalts and andesites similar in trace element composition to continental bholeiitic sequences. The Burnt Lake felsic pyroclastic suite comprises rhyolitic pyroclastics having major and trace element compositions that suggest that they were derived from cnastcil melts. Rare earth element models suggest that the Burnt Lake back-arc tholeiitic rocks were fomed by fractional crystallization of mafic magmas derived by approximately 5% partial melting of an amphibole-bearing depleted mantle, enriched in light rare earth elements by a subduction component. The modelling also suggests that the Burnt Lake continental tholeiitic rocks were formed by contamination -fractional crystallization of mixtures of mafic magmas, derived by -3% partial melting of the subduction-modified source, and rhyolitic crustal melts. These models are consistent with the suggestion that the Belmont Domain of the Central Metasedimentary Belt formed as a back-arc basin by attenuation of preexisting continental crust above a westerly dipping subduction zone.RQurnC : Trois suites de roches volcaniques intimement interstratifikes prbentent, chacune, une signature gkochimique distinctive dans la rkgion de Burnt Lake, Domaine Belmont de la Ceinture centrale de mktaskdiments, et leur Mtrogenkse a pu Ctre dkterminke. La suite tholkiitique d'arrikre-arc a Burnt Lake est formke de basaltes ayant une composition en klkments traces similaire a celle des basaltes tholCiitiques dCposCs dans les bassins d'arrikre-arc dCvelopp5s dans une croQte continentale. Tmdis que Ia suite tholkiitique continentale Burnt Lake comprend des basdtes et des andksites, avec des compositions en klkments traces similaires aux skquences tholkiitiques continentales. La suite pyroclastique felsique i i Burnt Lake inclut des pyroclastites rhyolitiques, avec des compositions en Clkrnents rnajeures et em traces reflktant une origine magrnatique crustale. Les modkles fondks sur les analyses des terres rares suggkrent que les roches tholkiitiques d'arrihre-arc a Burnt Lake furent formCes par cristallisation fractiomde de magmas mfiques, dkrivks approximativement de 5% de fusion partielle d'un manteau appauvri contenant des amphiboles, et enrichi en terres rares lkghres par un composant awompagnant la subduction. La modklisation sugg8re en outre que les roches tholkiitiques continentdes 1 Burnt Lake sont le rksultat d'une contamination -cristallisation fractionnee de melanges de magmas mfiques, dkrivks de -3% de fusion prtielle d'un matkriel modifid par subduction, et de magmas rhyolitiques crustaux.Ces modhles sont en accord avec la suggestion que le Domaine Belmont, ...

The Cuyano proto-ocean between the Chilenia and Cuyania terranes: rifting and plume interaction during the Neoproterozoic – early Palaeozoic evolution of the SW Gondwana margin

“…This agrees with predictions from computational modelling and experimental data supporting the theory that mantle plumes may be laterally zoned up to a length of 1000 km, and may exhibit a compositionally enriched central portion with a more depleted outer region (Jones et al 2016). Lambert et al (1988); Smith et al (1997); Goldberg & Dallmeyer (1997); Fisher et al (2010). Dashed lines indicating the field for southern Appalachian from Fullagar et al (1997).…”

Oxygen-isotope constraints on terrane boundaries and origin of 1.18–1.13 Ga granitoids in the southern Grenville Province

“…The Elzevir terrane is divided into several domains (Easton, 1992) that are interpreted as parts of an attenuated (and rifted) marginal basin developed at the edge of pre-Grenvillian Laurentia (e.g., Pehrsson et al, 1996;Smith et al, 1997), or as amalgamated volcanic arc terranes (Carr et al, 2000). The Sharbot Lake domain is the southeasternmost of these divisions (Fig.…”